JP2007245901A - Vehicular motion control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make appropriate the intervention timing of vehicle motion control for assisting the driving operation of a driver in response to a variation of a wheel road surface state such as a road surface friction coefficient. <P>SOLUTION: A wheel road surface state presumption means 23 for presuming a road surface friction coefficient, i.e., the wheel road surface state from self-aligning torque detected by a torque detection means 22 and a presumed motion state amount presumed by a vehicle motion state presumption means 13 based on a previously set tire model is provided. A parameter setting means 26 for changing the cornering power Kf, Kr of the tire, i.e., a parameter relating to a vehicle motion model of the vehicle motion state presumption means 13 according to the presumed road surface friction coefficient; and an intervention threshold value setting means 27 for changing the intervention threshold value of a control intervention determination means 16 according to the road surface friction coefficient are provided. Thereby, the road surface friction coefficient can be accurately presumed even if the vehicle motion state is stable. Further, since the parameter of the vehicle motion model is changed according to the road surface friction coefficient and the control intervention threshold of the vehicle motion is changed, proper control intervention timing can be accomplished. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle motion control device, and more particularly to a vehicle motion control device that supports a driver's driving operation in response to a change in a wheel road surface state and stabilizes the vehicle motion.

  As such a vehicle motion control device, conventionally, the motion state of the vehicle is detected by a sensor, the vehicle motion intended by the driver is estimated as the reference vehicle motion, and the actual vehicle motion is determined by the side slip of the vehicle. In the case where the vehicle motion is different from the vehicle motion, the brakes of each wheel are controlled so that the vehicle motion does not deviate from the reference vehicle motion.

  By the way, since the vehicle moves by transmitting force from the wheel to the road surface, the vehicle movement state greatly depends on the wheel road surface state which is a contact state between the wheel and the road surface. In particular, since the contribution to the vehicle motion is greatly influenced by the road surface friction coefficient, the following description will be made using the road surface friction coefficient as an amount representing the contact state between the wheel and the road surface.

  Patent Document 1 proposes an apparatus that performs vehicle motion control in consideration of a difference in vehicle motion state due to a road surface friction coefficient. According to this vehicle motion control device, the road surface friction coefficient is estimated, and the threshold value of the control intervention by the vehicle motion control device is changed based on the estimated road surface friction coefficient. The means for estimating the road surface friction coefficient is estimated based on the lateral acceleration detected by the lateral acceleration sensor when the steering angle detected by the steering angle sensor is equal to or greater than a certain value.

  That is, the ideal control intervention timing by the vehicle motion control device needs to correspond to a change in the road surface friction coefficient. For example, the control intervention threshold is set to be low when the road surface friction coefficient is likely to be unstable even when the operation amount is small. On the other hand, when the road surface friction coefficient is high so that the vehicle motion state does not become unstable with a slight change, it is desirable to increase the control intervention threshold. In this respect, the conventional example described in Patent Document 1 is preferable in that the road surface friction coefficient is estimated based on the lateral acceleration, and the control intervention threshold is set using the estimated road surface friction coefficient.

  Patent Document 2 describes a method of estimating a road surface friction coefficient based on a torque around a wheel turning axis at the time of turning in a steer-by-wire vehicle that performs steering control for each wheel. That is, the side slip angle, which is the angle formed by the torque generated around the wheel turning shaft during actual turning and the direction of the steered wheel and the vehicle traveling direction, is estimated, and the reference is determined from the estimated side slip angle. The torque (self-aligning torque) generated around the wheel turning shaft is set. Then, the self-aligning torque is compared with the torque generated around the wheel turning shaft during actual turning to estimate the grip state of the wheel, and the steering angle and braking force are controlled based on the grip margin of each wheel. I am doing so.

Japanese Patent No. 312395 JP 2004-130965 A

  By the way, as described in Patent Document 1, the road surface friction coefficient estimated by the lateral acceleration cannot be accurately estimated unless the state in which the lateral force that can be generated by the wheel approaches saturation. However, when the lateral force is saturated, the vehicle motion tends to be nonlinear and unstable, and there is a risk of deviating from the reference vehicle motion. Therefore, in the method of Patent Document 1 in which the control intervention is determined based on the road friction coefficient estimated by the lateral acceleration, the control intervention timing may be too late.

  On the other hand, if the road surface friction coefficient is estimated before the lateral force is saturated, the lateral acceleration at that time is in the process of increasing, and therefore an accurate road surface friction coefficient cannot be estimated. For example, if the road friction coefficient is estimated to be lower than the actual one, the intervention threshold value is set to be low accordingly, so that the vehicle motion control may intervene regardless of the motion state that does not require the vehicle motion control intervention. is there. Such early intervention has the problem that it is difficult for the driver to drive. Therefore, in order to avoid early intervention, it is conceivable to estimate the road surface friction coefficient based on the lateral acceleration higher. However, if the road friction coefficient is estimated to be high, the vehicle movement control may not intervene even if the vehicle movement becomes unstable when the actual road friction coefficient is low, and the control intervention timing will be delayed. is there.

  Further, in the technique of Patent Document 1, since the influence of the road surface friction coefficient is not taken into account in estimating the actual vehicle motion state, the estimated vehicle motion state amount may differ from the actual depending on the wheel road surface state. is there. For example, the vehicle motion state amount estimated on the assumption that the road surface friction coefficient is high may be smaller than the actual vehicle motion state amount in a scene where the road surface friction coefficient is low. Therefore, even though a large amount of vehicle motion state has actually occurred and the vehicle behavior has become unstable, the vehicle motion state amount is estimated as a small value, so it is determined that the vehicle motion is stable. However, there is a problem that the vehicle motion control intervention is delayed from the appropriate timing.

  Further, even if one of the intervention threshold value and the motion state quantity estimated value is optimized, vehicle motion control intervention cannot be performed at an appropriate timing under various driving conditions.

  On the other hand, in the prior art described in Patent Document 2, since the grip state of each wheel must be obtained and the vehicle motion must be controlled by controlling each wheel independently, the control becomes complicated. In addition, there are problems such as an increase in sensors and actuators for vehicle motion control.

  The problem to be solved by the present invention is to optimize the intervention timing of the vehicle motion control that supports the driving operation of the driver in response to a change in the wheel road surface state such as the road surface friction coefficient.

  In order to solve the above problems, the present invention provides vehicle motion control means for controlling the motion of a vehicle, detection means for detecting an operation amount of the vehicle motion and a motion state amount of the vehicle by a driver, and the operation amount. Vehicle motion state amount estimating means for estimating at least one estimated motion state amount from the driving state amount based on a vehicle motion model, and driving based on a linear model from the operation amount, the driving state amount, and the estimated motion state amount The control amount of the vehicle motion control means is reduced so as to reduce the difference between the reference motion generation means for estimating the reference motion state quantity of the vehicle intended by the person and the reference motion state quantity corresponding to the estimated motion state quantity. Vehicle motion by the vehicle motion control amount setting means when a difference between the vehicle motion control amount setting means to be set and the reference motion state quantity corresponding to the estimated motion state quantity exceeds a set intervention threshold Target vehicle motion control device and a control intervention decision means for performing control intervention.

  In particular, the vehicle motion control device of the present invention includes any one of the torque detected by the torque detection means for detecting the torque generated around the wheel turning shaft, the estimated motion state quantity, and the motion state quantity detected by the detection means. From the other, a wheel road surface state estimating unit that estimates a state of a wheel and a road surface based on a preset tire model, and the vehicle motion state estimating unit according to the wheel road surface state estimated by the wheel road surface state estimating unit Parameter setting means for changing parameters relating to the vehicle motion model, and intervention threshold setting means for changing the intervention threshold of the control intervention determination means according to the wheel road surface state estimated by the wheel road surface state estimation means It is characterized by that.

  Because of such characteristics, according to the present invention, the torque (self-aligning torque) generated around the wheel turning shaft is detected, and this self-aligning torque and a preset estimated motion state quantity are detected. Since the wheel road surface state estimating means for estimating the wheel road surface state (for example, the road surface friction coefficient) based on the preset tire model is provided from the value of the state of motion state, the vehicle motion state is stable. Even if it exists, a wheel road surface state can be estimated with high precision. In addition, since the parameters (for example, tire cornering powers Kf and Kr) of the calculation model of the vehicle motion state quantity estimating means whose value changes depending on the road surface condition are set, it is estimated by the vehicle motion state quantity estimating means. The accuracy of the estimated motion state quantity is improved. At the same time, because the intervention threshold of the vehicle movement control intervention judgment means is changed based on the highly accurate estimated wheel road surface condition, appropriate control intervention timing according to the wheel road surface state and the estimated movement state quantity is realized. can do.

  In this case, the control amount set by the vehicle motion control amount setting unit can be changed also by the wheel road surface state estimated by the wheel road surface state estimation unit.

  In addition, the control intervention determination means, when the current exercise state continues even if the difference between the estimated exercise state amount and the reference exercise state amount does not exceed a set intervention threshold, When it is predicted that the movement intended by the person is not realized, vehicle movement control intervention by the vehicle movement control means can be performed. According to this, by predicting that future vehicle motion will deviate from the normative motion, even if the vehicle is in a stable motion state, it is possible to prevent the vehicle motion from becoming unstable by performing intervention control. Can do.

  Further, the wheel road surface state estimating means estimates the wheel road surface state based on a preset tire model from the torque detected by the torque detecting means and the estimated motion state quantity or the detected motion state quantity. A first wheel road surface state estimating unit; and a second wheel road surface state estimating unit that estimates the wheel road surface state based on the motion state quantity of the vehicle detected by the detecting unit, and starting steering. Until the vehicle motion control intervention, the parameters and the intervention threshold are changed according to the wheel road surface state estimated by the first wheel road surface state estimation means until the vehicle motion is stabilized after the vehicle motion control intervention. Has wheel road surface state selecting means for changing the parameter and the intervention threshold according to the wheel road surface state estimated by the second wheel road surface state estimating means. It can be configured.

  Alternatively, the wheel road surface state estimating means changes the parameter and the intervention threshold according to the estimated wheel road surface state from the start of steering until the vehicle motion control intervention, and performs vehicle motion control. The parameter and the intervention threshold value can be held at the previous values until the vehicle motion is stabilized after the intervention.

  In any of the above cases, the estimated motion state quantity can be at least one of a vehicle slip angle and a yaw rate.

  ADVANTAGE OF THE INVENTION According to this invention, the intervention timing of the vehicle motion control which supports a driver | operator's driving operation corresponding to the change of wheel road surface conditions, such as a road surface friction coefficient, can be optimized.

  Hereinafter, a vehicle motion control device of the present invention will be described based on embodiments.

  FIG. 1 shows a block diagram of an embodiment of a vehicle motion control device of the present invention. As shown in FIG. 1, the vehicle motion control apparatus of the present embodiment includes an operation amount detection means 11 that detects an operation amount of a steering system of a vehicle operated by a driver, and an exercise state amount that detects a vehicle motion state amount. Detecting means 12, vehicle motion state quantity estimating means 13, reference vehicle motion generating means 14, vehicle motion control amount setting means 15, control intervention determining means 16, vehicle motion control means 17, switching means 18, A road surface friction coefficient estimating means 20 and a parameter / intervention threshold setting means 21 are provided.

  The operation amount detection unit 11 includes a sensor that detects an operation amount (steering angle, steering torque, etc.) operated by the driver. The motion state quantity detection means 12 includes a sensor that detects a vehicle speed, a yaw rate (rotational angular velocity of the vehicle), acceleration, and the like, which are vehicle motion state quantities.

  The vehicle motion state quantity estimation means 13 is directly detected by the motion state quantity detection means 12 based on the operation amount detected by the operation quantity detection means 11 and the vehicle motion state quantity detected by the motion state quantity detection means 12. Other vehicle motion state quantities that cannot be estimated are estimated. Specifically, for example, an observer having an arithmetic expression of a motion model of the vehicle estimates the side slip angle β of the vehicle body, which is an angle between the traveling direction of the vehicle body and the direction of the vehicle body.

  The normative vehicle motion generation means 14 includes the operation amount detected by the operation amount detection means 11, the vehicle motion state quantity detected by the motion state quantity detection means 12, and the vehicle motion estimated by the vehicle motion state quantity estimation means 13. Based on the state quantity (eg, side slip angle β), the driver's intended vehicle motion is predicted by a well-known linear model to generate the driver's intended reference vehicle motion (eg, side slip, yaw rate, etc.). It has become.

  The vehicle motion control amount setting means 15 compares the actual vehicle motion state quantity estimated by the vehicle motion state quantity estimation means 13 with the reference vehicle motion output from the reference vehicle motion generation means 14, and compares the actual vehicle motion state. The control amount when the vehicle motion control apparatus according to the present embodiment intervenes is determined so that the state amount matches the reference vehicle motion. When the vehicle motion control device according to this embodiment intervenes, the output of the vehicle motion control amount setting means 15 is output to the vehicle motion control means 17 via the switching means 18. The vehicle motion control means 17 is a means for controlling vehicle motion such as braking force, throttle opening, shift (gear ratio), steering force weight, and the like.

  On the other hand, the switching means 18 is switched by the control intervention judgment means 16. The control intervention judgment means 16 controls the vehicle motion control means 17 by whether or not to intervene vehicle motion control by the vehicle motion control apparatus according to the present embodiment, that is, by the control amount set by the vehicle motion control amount setting means 15. Whether or not. For this purpose, the control intervention determination unit 16 compares the actual vehicle motion state amount estimated by the vehicle motion state amount estimation unit 13 with the reference vehicle motion output from the reference vehicle motion generation unit 14, and compares the actual vehicle motion state amount with the actual vehicle motion state amount. When the motion state quantity deviates from the reference vehicle motion beyond the control intervention threshold, vehicle motion control intervention is performed. In short, the control intervention judgment means 16 makes a control intervention judgment according to the control intervention threshold set by the parameter / intervention threshold setting means 21 in order to prevent frequent intervention in situations where vehicle motion control is unnecessary. Yes. Details thereof will be described later.

  The road surface friction coefficient estimating means 20 is an embodiment of the wheel road surface state estimating means according to the present invention, and estimates the road surface friction coefficient μ which is one of physical quantities representing the wheel road surface state. Here, the wheel road surface state is not limited to the road surface friction coefficient μ, and a physical quantity correlated with the road surface friction coefficient μ such as a contact area between the wheel and the ground or a physical quantity equivalent to the road surface friction coefficient μ can be used.

  The parameter / intervention threshold setting means 21 is an embodiment of the wheel road surface state estimating means, and the parameter / intervention threshold setting means 21 is based on the road surface friction coefficient μ estimated by the road surface friction coefficient estimating means 20. The parameters included in the observer's arithmetic expression of the vehicle motion state quantity estimating means 13 for estimating the state quantity are obtained, and the control intervention threshold value is obtained. Then, the obtained parameters are set in the vehicle motion state quantity estimating means 13, and the control intervention threshold necessary for determining the control intervention is set in the control intervention determining means 16.

  Next, referring to FIG. 2, one embodiment of the detailed configuration of the road surface friction coefficient estimating means 20 and the parameter / intervention threshold setting means 21 as an embodiment of the wheel road surface state estimating means according to the characterizing portion of the present invention. Will be described. As shown in FIG. 2, the road surface friction coefficient estimating means 20 of this embodiment includes a first road surface friction coefficient estimating means 23 and a second road surface friction coefficient estimating means 24. The first road surface friction coefficient estimating means 23 includes the self-aligning torque Ts detected by the self-aligning torque detecting means 22 and the motion state quantity (vehicle speed, yaw rate (vehicle rotational angular velocity) detected by the motion state quantity detecting means 12. ), Acceleration, etc.) or the vehicle driving state quantity estimated by the vehicle motion state quantity estimating means 13 (for example, the side slip angle) is estimated. The second road surface friction coefficient estimating means 24 estimates the road surface friction coefficient μ2 based on the lateral acceleration detected by the driving state quantity detecting means 12.

  The self-aligning torque detecting means 22 directly detects the self-aligning torque Ts using a sensor such as a six-component force meter constituted by, for example, a strain gauge or a piezoelectric element attached to a wheel. . Here, the self-aligning torque Ts is a well-known physical quantity as described in Patent Document 2, and is a torque generated around the turning axis of the tire (wheel), which reduces the side slip angle β of the tire. This is the torque that acts in the direction to be generated. The self-aligning torque Ts is expressed as a product of a lateral force acting on the wheel and a pneumatic trail. Therefore, the self-aligning torque Ts has a higher sensitivity that affects the change in the road surface friction coefficient than the lateral force. Therefore, it is possible to accurately estimate the road surface friction coefficient at an early stage before the vehicle motion becomes unstable.

  From this, the first road surface friction coefficient estimating means 23 of the present embodiment uses a tire model that represents the relationship between the road surface friction coefficient, the self-aligning torque Ts, and the side slip angle β (for example, the front wheel side slip angle βf). The road surface friction coefficient μ1 is estimated. Here, the side slip angle β is obtained by the vehicle motion state quantity estimating means 13. The tire model should be a well-known brush model that is modeled by arranging an infinite number of independent elastic bodies in the circumferential direction of the elastically deforming wheel around the ring corresponding to the wheel rim or tread base. Can do. For example, the first road surface friction coefficient estimating means 23 can be applied by mapping the relationship among the road surface friction coefficient μ1, the self-aligning torque Ts, and the side slip angle β calculated based on the brush model. Alternatively, the brush model equation can be directly solved with respect to the road surface friction coefficient μ1, and the road surface friction coefficient μ1 can be obtained as an expression of the self-aligning torque Ts and the front wheel side slip angle βf.

  By the way, when the vehicle motion is determined to be unstable during or after the intervention of the vehicle motion control, it is predicted that the vehicle motion is in a non-linear state. In such a case, the accuracy of the vehicle motion state quantity estimated by the vehicle motion state quantity estimation means 13 cannot be guaranteed. Therefore, the accuracy of the road surface friction coefficient μ1 estimated by the first road surface friction coefficient estimating means 23 based on the front wheel side slip angle βf and the self-aligning torque Ts cannot be guaranteed.

  Therefore, in this embodiment, in addition to the first road friction coefficient estimating means 23 based on the self-aligning torque, a second road friction coefficient estimating means 24 based on the lateral acceleration is separately provided. The second road surface friction coefficient estimating means 24 takes in the lateral acceleration detected by the motion state quantity detecting means 12 to estimate the road surface friction coefficient, obtains a maximum value of the estimated road surface friction coefficient, and the obtained maximum value is When it becomes larger than the road surface friction coefficient estimated at the time of the previous calculation, the higher road surface friction coefficient μ2 is output.

  The road surface friction coefficient selection means 25 switches the road surface friction coefficient μ1 to the road surface friction coefficient μ2 at the time of control intervention based on the control intervention determination signal input from the control intervention determination means 16, and sets parameter / intervention threshold value setting means. 21 is output.

  On the other hand, the parameter / intervention threshold setting means 21 includes a parameter setting means 26 and an intervention threshold setting means 27. The parameter setting means 26 sets parameters included in the observer of the arithmetic expression of, for example, the vehicle body slip angle β estimated by the vehicle motion state quantity estimation means 13 according to the road surface friction coefficient μ1 or μ2 output from the road surface friction coefficient selection means 25. It is supposed to be. Further, the intervention threshold setting means 27 is configured to set the intervention threshold λ of the control intervention determination means 16. Here, the parameters used for the calculation of the vehicle body side slip angle β are the front wheel cornering power Kf and the rear wheel cornering power Kr of the vehicle model. The cornering power is a value indicating the generated lateral force per unit side slip angle of the wheel, and changes depending on the road surface friction coefficient.

  The detailed configuration of the present embodiment configured as described above will be described below together with the operation. In this embodiment, basically, an intervention threshold value λ for determining intervention of vehicle motion control is set based on the road surface friction coefficient μ1 obtained by the first road surface friction coefficient estimating means 23 using the self-aligning torque Ts. When the difference between the actual vehicle motion state quantity and the reference vehicle motion exceeds the intervention threshold, the intervention timing for performing the vehicle motion control is appropriately controlled by the control amount set by the vehicle motion control amount setting means 15. I have to.

  As shown in FIG. 3, as an example of the vehicle motion state quantity intervention threshold λ for determining the control intervention timing, the actual vehicle body side slip angle β estimated by the vehicle motion state quantity estimation unit 13, the reference vehicle motion generation unit 13, or the like. The difference Δβ from the normative vehicle body side slip angle generated by can be used. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the vehicle body side slip angle β or the difference Δβ. For the sake of explanation, the vehicle has a high road surface friction coefficient μ before steering is started, and the estimated value of the vehicle motion state at this time is shown by a curve 30 in FIG. Further, a curve 31 in FIG. 3 shows a time change of an example of an actual vehicle motion state quantity.

  FIG. 4 shows an example of the relationship between the road surface friction coefficient μ (μ1, μ2) and the front and rear wheel cornering powers Kf, Kr of the vehicle model used by the observer in the vehicle motion state estimation means 13. The relationship between the road surface friction coefficient μ and the front and rear wheel cornering powers Kf and Kr in FIG. 4 can be mapped in advance. The first road surface friction coefficient estimating means 23 estimates the road surface friction coefficient μ1 using the self-aligning torque Ts while the vehicle motion shown in FIG. 3 is stable. Then, the parameter setting means 26 obtains the front and rear wheel cornering powers Kf and Kr from FIG. 4 based on the estimated road friction coefficient μ 1 and sets them in the vehicle motion state quantity estimating means 13. That is, as shown in FIG. 4, the values of the cornering powers Kf and Kr of the front and rear wheels are set large when the road surface friction coefficient μ is high, and are set small when the road friction coefficient μ is low. This means that the estimated value of the side slip angle β does not increase immediately when the road surface friction coefficient μ is high, and conversely, the estimated value of the side slip angle β tends to increase when the road surface friction coefficient μ is low. The values of the front and rear wheel cornering powers Kf and Kr are determined.

  Thereby, when the estimated value of the vehicle driving state quantity before the parameter change by the vehicle motion state quantity estimating means 13 is different from the actual vehicle driving state quantity of the curve 31, as shown by the curve 30 in FIG. When the parameter is changed to the parameter corresponding to the road surface friction coefficient μ1, as shown by the curve 32, the estimated value of the vehicle operating state quantity after the parameter change is obtained. That is, the estimation accuracy of the vehicle motion state quantity estimation unit 13 is improved, and the curve 31 and the curve 32 are in a relationship that is identical or approximate. As a result, the deviation of the control intervention timing due to the estimation error of the vehicle driving state quantity can be corrected.

  On the other hand, the intervention threshold value λ of the control intervention determination means 16 is also variably set according to the road surface friction coefficient μ. FIG. 5 shows the relationship between the road surface friction coefficient μ and the intervention threshold value λ. As shown in the figure, the intervention threshold value λ is set so as to increase on the side where the road surface friction coefficient μ is high, and conversely, is set so as to decrease on the low side. As the relationship between the intervention threshold value λ and the road surface friction coefficient μ, a map mapped in advance as in FIG. 4 can be used.

  In this way, by setting the intervention threshold value λ variably according to the road surface friction coefficient μ, as shown in FIG. 3, when the road surface friction coefficient μ becomes small, the intervention threshold value 33 at high μ is set to the intervention value at low μ. The threshold value 34 can be varied. As a result, as shown in FIG. 3, the intervention timing t2 after the parameter change approaches the appropriate intervention timing t0 with respect to the intervention timing t1 before the parameter change, and the delay of the control intervention timing can be corrected.

  As described above, two setting changes of the parameters Kf and Kr and the intervention threshold value λ are performed before the vehicle motion control intervention, so that the vehicle motion becomes stable at various times before the vehicle motion becomes unstable in various vehicle motion states. Vehicle motion control can be intervened.

  6 and 7 show flowcharts of processing procedures of the vehicle motion control apparatus of FIG. 1 embodiment. The flowcharts of FIGS. 6 and 7 are periodically executed while the vehicle is running. First, in step S101, the vehicle motion state estimation unit 13 reads the operation amount such as the turning angle δf and the operation torque operated by the driver from the operation amount detection unit 11 attached to the vehicle, and also the motion state. The vehicle motion state quantities such as the vehicle speed, the yaw rate γ, and the lateral acceleration ay are read from the quantity detection means 12. Next, in step S102, the vehicle motion state quantity estimating means 13 uses the observer from the steered angle δf, lateral acceleration ay, and yaw rate γ that has been taken in, and the side slip angle β of the vehicle body, which is one of the vehicle motion state quantities. Is estimated. In the next step S103, as shown in FIG. 7, the set values of the parameters Kf, Kr and the intervention threshold λ are changed by the road surface friction coefficient μ obtained by the parameter / intervention threshold setting means 21, and the vehicle motion state quantities are respectively changed. It is output to the estimation means 13 and the control intervention judgment means 16. Next, in step S104, the reference vehicle motion generation unit 14 reads the operation amount such as the turning angle δf and the operation torque from the operation amount detection unit 11, and the vehicle speed, yaw rate γ, lateral force from the motion state amount detection unit 12. The vehicle motion state quantity such as acceleration ay is read, and the estimated motion state quantity (eg, side slip angle, wheel load, roll angle, etc.) is read from the vehicle motion state quantity estimation means 13, and the vehicle motion state quantity is determined according to the vehicle linear model. The standard vehicle motion state quantity is generated by predicting the side slip angle β which is one of the following.

  Here, the vehicle motion state quantity estimation means 13 estimates the current estimated motion state quantity (side slip angle, wheel load, roll angle, etc.) that is difficult to measure with a sensor, using an observer. Further, by comparing the estimated estimated motion state quantity with the actual vehicle output, it is corrected to a value closer to the actual vehicle motion state quantity. On the other hand, the linear model of the reference vehicle motion generation means 14 is based on the ideal state of vehicle motion or the amount of vehicle motion state intended by the driver (for example, yaw rate, side slip angle, etc.). It is estimated from the amount of movement or the amount of motion detected by the sensor. The difference between the estimated value by the reference vehicle motion generation unit 14 and the estimated value by the observer of the vehicle motion state estimation unit 13 is an ideal value (linear motion) based on a linear model, and the actual vehicle travel Depending on the state, the value will be different. Therefore, when determining the ideal vehicle motion state amount, the reference vehicle motion generation unit 14 reads an amount (for example, wheel load) that changes depending on the vehicle motion state from the vehicle motion state amount estimation unit 13 to obtain the vehicle motion state amount. The model is corrected according to the motion state by reflecting in the linear model.

  Next, in step S105, the vehicle motion control amount setting means 15 estimates the reference vehicle motion state quantity (for example, the side slip angle β) generated by the reference vehicle motion generation means 14 and the vehicle motion state quantity estimation means 13. An error (eg, Δβ) with respect to the actual vehicle motion state quantity (eg, side slip angle β) obtained is obtained, and a control amount (eg, brake) of each actuator of the vehicle motion control means 17 necessary to reduce the error is obtained. Control amount). Next, the process proceeds to step S106, and the control intervention determination means 16 determines whether or not the vehicle motion control intervention is necessary from the actual vehicle motion state quantity and the reference vehicle motion state quantity. That is, in the present embodiment, the determination is made based on whether or not the difference | Δβ | between the actual vehicle body side slip angle β and the reference vehicle body side slip angle exceeds the variably set intervention threshold λ. In the case of the difference | Δβ |> λ, although not shown in the figure, the flag “in control intervention” is set and the process proceeds to step S107. In step S <b> 107, the switching means 18 is turned on and the control amount that is the output of the vehicle motion control amount setting means 15 is supplied to the vehicle motion control means 17. Thereby, the intervention of the vehicle motion control is executed, and the process returns to step S101 and the same processing is repeated. On the other hand, if the difference | Δβ | ≦ λ is determined in step S106, although not shown, the “control intervention in progress” flag is turned off, and no intervention of vehicle motion control is required, and the process returns to step S101.

  A detailed processing procedure for setting change by the road surface friction coefficient μ in step S103 of FIG. 6 will be described along the flowchart shown in FIG. First, in step S201, the control intervention determination unit 16 includes at least the turning angle δf, the lateral acceleration ay, and the yaw rate γ output from the operation amount detection unit 11, the movement state amount detection unit 12, or the vehicle movement state amount estimation unit 13. Based on one, it is determined whether or not the vehicle is turning. In this determination, when each value of the turning angle δf, the lateral acceleration ay, and the yaw rate γ is lower than a preset set value, it is determined that the vehicle is in a straight traveling state. When the vehicle is in the straight traveling state, the process proceeds to step S202, where the control intervention determination unit 16 sends a control intervention determination signal to the road surface friction coefficient selection unit 25, and the previously estimated road surface friction coefficient μ, parameters Kf, Kr, intervention. The previous value of the threshold λ is held as the current value, and the process returns to step S104 in FIG. That is, the road surface friction coefficient μ, the observer parameters Kf and Kr, and the intervention threshold value λ are not changed.

  On the other hand, if it is determined in step S201 that any one of the turning angle δf, the lateral acceleration ay, and the yaw rate γ is greater than or equal to a preset value, it is determined that the vehicle is turning. The process proceeds to S203. In step S203, the control intervention determination means 16 determines whether or not the vehicle is in a stable motion state based on whether or not the actual vehicle motion state quantity (for example, the side slip angle β or Δβ) deviates from the reference motion state quantity. To do. For example, based on the “control intervention in progress” flag, when the vehicle motion control intervention is not performed or after the vehicle motion control intervention is canceled, the actual vehicle motion state quantity deviation amount is less than or equal to the set value. At this time, it is determined that the vehicle is in a stable state, and the process proceeds to step S204. When the deviation exceeds a set value, it is determined that the movement is unstable.

  In step S204, the first road surface friction coefficient estimating means 23 reads the self-aligning torque Ts from the self-aligning torque detecting means 22, and also the motion state quantity (for example, the stable motion determination estimated by the vehicle motion state estimating means 13 (for example, , Side slip angle) is taken in, and the process proceeds to step S205 to estimate the road surface friction coefficient μ1 as described above. Next, the process proceeds to step S208, where the parameter setting means 26 calculates the front and rear wheel cornering powers Kf and Kr, which are the parameters of the observer of the vehicle motion state quantity estimation means 13, based on the estimated road surface friction coefficient μ1 from FIG. Change the settings when prompted. Next, in step S209, the intervention threshold setting unit 27 obtains the intervention threshold λ corresponding to the road surface friction coefficient μ from FIG. 5 and variably sets the intervention threshold λ of the control intervention determination unit 16.

  On the other hand, in step S203, the control intervention determination unit 16 determines that the actual vehicle motion state quantity (for example, the side slip angle β or Δβ) deviates from the reference motion state quantity during or after the vehicle motion control intervention. When the amount exceeds the set value, it is determined as an unstable movement state. When it is determined that the driving state of the vehicle is unstable, the road surface friction coefficient selection means 25 replaces the road surface friction coefficient used for intervention control with the road surface friction coefficient μ1 obtained by the first road surface friction coefficient estimation means 23. The road surface friction coefficient μ2 obtained by the second road surface friction coefficient estimating means 24 is selected. Then, the process proceeds to steps S206 and S207, and the parameter setting means 26 uses the road surface friction coefficient μ2 obtained by the second road surface friction coefficient estimation means 24 and uses the front and rear wheel cornering which is an observer parameter of the vehicle motion state quantity estimation means 13. The powers Kf and Kr and the intervention threshold value λ are variably set. That is, in step S206, the second road surface friction coefficient estimating unit 24 reads the maximum value of the lateral acceleration output from the lateral acceleration sensor of the motion state quantity detecting unit 12, and in step S207, calculates the current road surface friction coefficient μa. Then, the road surface friction coefficient estimated value μb calculated at the previous processing is compared, and if it is determined that μa> μb, μa is set as the road surface friction coefficient μ.

  As described above, the estimation method of the road surface friction coefficient is switched according to the stable state or the unstable state of the vehicle, thereby reducing erroneous estimation when the vehicle is unstable. After the road surface friction coefficient μ2 is set, the cornering powers Kf and Kr that are the parameters of the observer of the vehicle motion state estimation means 13 and the intervention threshold value of the control intervention judgment means 16 are set in steps S208 and S209 as described above. λ is changed and set, and the process returns to step S104 in FIG.

  As described above, in this embodiment, while the vehicle motion state is stable, the road surface friction coefficient μ1 is estimated using the self-aligning torque Ts, and the vehicle motion state is based on the road surface friction coefficient μ1. Since the cornering powers Kf and Kr, which are parameters of the calculation model of the quantity estimation means 13, are set, the accuracy of the estimated value of the vehicle motion state quantity can be improved. In addition, since the intervention threshold value λ of the vehicle motion control intervention determination means 16 is changed based on the estimated road friction coefficient μ1, an appropriate control intervention timing in accordance with the road surface friction coefficient can be realized.

  In the above embodiment, the example in which the self-aligning torque Ts is directly measured by the sensor attached to the steering system has been described. However, the self-aligning torque detecting means 22 of the present invention is not limited to this. For example, the self-aligning torque detecting means 22 measures the axial force of the steering column by means of an axial force detecting means constituted by a sensor or the like attached to the tie rod end, and estimates the self-aligning torque based on the measured value. Can be.

  Further, the self-aligning torque Ts can be calculated based on a hydraulic pressure measured by a hydraulic pressure detection means in a steering system having a hydraulic power steering device and based on the detected hydraulic pressure value.

  The self-aligning torque Ts can be estimated from the steering torque and assist torque of the driver by a steering device having an electric power steering device.

  In the above embodiment, the second road surface friction coefficient estimating means is used when the actual vehicle motion (for example, the side slip angle β or Δβ) deviates from the reference motion by more than a set value during or after the vehicle motion control intervention. 24, the road surface friction coefficient μ2 is shown. However, in the present invention, instead of this, the value of the road surface friction coefficient μ1 estimated before the vehicle motion control intervention by the first road surface friction coefficient estimating means 23 is not changed even after the vehicle motion control intervention. You may make it keep holding.

  In the above-described embodiment, the road surface friction coefficient μ is not directly reflected on the vehicle motion control amount setting means 15. Instead, the road surface friction coefficient μ is transmitted to the vehicle motion control amount setting means 15. The control amount may be changed according to the road surface friction coefficient μ. For example, when the road surface friction coefficient μ is large, it is predicted that a large braking force will be obtained. Therefore, the set braking force is increased.

  In the above-described embodiment, the side slip angle Δβ is taken as an example of the state quantity referred to in order to determine the vehicle movement control intervention timing, but the present invention is not limited to this. For example, instead of the side slip angle Δβ, the difference Δγ between the yaw rate generated by the reference vehicle motion generation means 14 and the actual yaw rate, the derivative value of the side slip angle β or the yaw rate γ, or a combination of these, or addition You can use things that match.

  FIG. 8 shows a flowchart of a control procedure of another embodiment of the vehicle motion control device of the present invention. This embodiment differs from the first embodiment in that when the determination in step S106 in FIG. 6 is “no intervention”, vehicle motion prediction means (steps S301 to S303) and stable vehicle motion control amount setting means. The processing of (Steps S304 to S305) is performed.

  The vehicle motion prediction means is used when the turning motion predicted from the detected values of the operation amount detection means 11 and the motion state quantity detection means 12 and the vehicle motion state quantity estimated by the vehicle motion state quantity estimation means 13 is continued. Then, it is determined by predicting whether or not the turning motion can be realized on the road surface having the road surface friction coefficient μ1 by the self-aligning torque Ts. On the other hand, the stable vehicle motion control amount setting means is capable of controlling the throttle opening degree even when the vehicle motion is in a stable state when the result of prediction by the vehicle motion prediction means cannot realize the turning motion intended by the driver. The brake control, the shift control, etc. are performed to decelerate the vehicle so that the turning motion intended by the driver can be achieved. These control amounts are output to the vehicle motion control means 17.

  A detailed processing procedure of the present embodiment will be described with reference to FIG. In the figure, the same processing steps as those in the flowchart of FIG. The functions added in the present embodiment are steps S301 to S305 that are executed after it is determined in step S106 that the vehicle motion control is not intervened.

  If it is determined in step S106 that there is no vehicle motion control intervention, the process proceeds to step S301, and the lateral force of the front and rear wheels t time after the current time is obtained by calculation. That is, the lateral force Ff, Fr required for the front wheels and the rear wheels after a time t greater than 0 by the vehicle moving with the current operation amount and the movement state amount is obtained by the following equation (1). In the equation, βf and βr are estimated side slip angles of the front wheels and the rear wheels, respectively, and βf ′ and βr ′ are differential values of estimated side slip angles of the front wheels and the rear wheels, respectively.

Ff = Kf (βf + βf′t)
Fr = Kf (βr + βr′t) (1)

  In step S302, the maximum lateral forces Ffmax and Frmax that can be generated on the front and rear wheels with the currently estimated road friction coefficient μ are obtained by the following equation (2). In the equation, Mf and Mr are loads on the front and rear wheels, respectively, and g is a gravitational acceleration. The coefficients κf and κr are constants such that 0 <κf and κr <= 1.

Ffmax = κf · μ · Mf · g
Frmax = κr · μ · Mr · g (2)

  In step S303, if the condition of the following equation (3) is satisfied, it is determined that the vehicle motion remains stable even if the current motion is continued, and the control returns to step S101 without executing the control.

Ff ≦ Ffmax
And Fr ≦ Frmax (3)
On the other hand, if the condition of the following expression (4) is satisfied, it is determined that the target turn cannot be achieved if the current exercise is continued, and the process proceeds to step S304.

Ff> Ffmax
Or Fr> Frmax (4)
In step S304, a target deceleration amount is generated so that the target turning can be achieved, and a deceleration command is issued to the vehicle motion control means 17 in step S305 to decelerate. Thereafter, the process returns to S104 in FIG.

  According to the present embodiment, it is possible to perform control so that stable motion can be continued before vehicle motion becomes unstable.

It is a block block diagram of one Example of the vehicle motion control apparatus of this invention. FIG. 2 is a detailed block configuration diagram of a road surface friction coefficient estimating unit and a parameter / threshold setting unit in FIG. 1. It is a figure explaining the effect of vehicle motion control intervention timing optimization. It is a figure which shows an example which sets the parameters Kf and Kr based on the road surface friction coefficient (micro | micron | mu). It is a figure which shows an example which sets the intervention threshold value (lambda) based on the road surface friction coefficient (micro | micron | mu). It is a flowchart which shows an example of the process sequence of the vehicle motion control apparatus of one Example of this invention. It is a flowchart which shows an example of the detailed process sequence of step S103 of FIG. It is a flowchart which shows an example of the process sequence of the vehicle motion control apparatus of the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Operation amount detection means 12 Motion state quantity detection means 13 Vehicle motion state quantity estimation means 14 Reference vehicle motion generation means 15 Vehicle motion control amount setting means 16 Control intervention judgment means 17 Vehicle motion control means 18 Switching means 20 Road surface friction coefficient estimation means 21 Parameter / intervention threshold setting means 22 Self-aligning torque detection means 23 First road friction coefficient estimation means 24 Second road friction coefficient estimation means 25 Road friction coefficient selection means 26 Parameter setting means 27 Intervention threshold setting means

Claims (6)

Vehicle motion control means for controlling the motion of the vehicle, detection means for detecting the amount of operation of the vehicle motion by the driver and the motion state quantity of the vehicle, and at least based on the vehicle motion model from the operation quantity and the driving state quantity A vehicle motion state amount estimating means for estimating one estimated motion state amount, and a reference motion state amount of the vehicle intended by the driver based on a linear model from the operation amount, the driving state amount, and the estimated motion state amount. Vehicle motion control amount setting means for setting a control amount of the vehicle motion control means so as to reduce a difference between the reference motion generation means to be estimated and the reference motion state quantity corresponding to the estimated motion state quantity; and the estimation Control intervention determination means for performing vehicle motion control intervention by the vehicle motion control amount setting means when a difference from the reference motion state quantity corresponding to the motion state quantity exceeds a set intervention threshold. The vehicle motion control device that,
From the torque detected by the torque detection means for detecting the torque generated around the wheel turning shaft, the estimated motion state quantity, and the motion state quantity detected by the detection means, the tire model is set in advance. A wheel road surface state estimating means for estimating the state of the wheel and the road surface based on, and a parameter for changing a parameter relating to the vehicle motion model of the vehicle motion state estimating means according to the wheel road surface state estimated by the wheel road surface state estimating means A vehicle motion control apparatus comprising: setting means; and intervention threshold setting means for changing the intervention threshold of the control intervention determination means in accordance with a wheel road surface state estimated by the wheel road surface state estimation means. The vehicle motion control device according to claim 1,
The vehicle motion control device, wherein the control amount set by the vehicle motion control amount setting means is changed according to the wheel road surface state estimated by the wheel road surface state estimation means. The vehicle motion control device according to claim 1,
The control intervention determination means, when the current exercise state is continued even if the difference between the estimated exercise state amount and the reference exercise state amount does not exceed a set intervention threshold, A vehicle motion control device that performs vehicle motion control intervention by the vehicle motion control means when an intended motion is predicted not to be realized. The vehicle motion control device according to any one of claims 1 to 3,
The wheel road surface state estimating means includes first wheel road surface state estimating means for estimating the wheel road surface state based on a tire model set in advance from the torque detected by the torque detecting means and the estimated motion state amount, Second wheel road surface state estimating means for estimating the wheel road surface state based on the amount of motion state of the vehicle detected by the detecting means, and from the start of steering until the intervention of vehicle motion control. The parameter and the intervention threshold are changed according to the wheel road surface state estimated by the one-wheel road surface state estimating unit, and the second wheel road surface state estimating unit estimates until the vehicle motion is stabilized after the vehicle motion control intervention. A vehicle motion control device comprising wheel road surface state selection means for changing the parameter and the intervention threshold according to the wheel road surface state. . The vehicle motion control device according to any one of claims 1 to 3,
The wheel road surface state estimating means changes the parameter and the intervention threshold according to the estimated wheel road surface state from the start of steering until the vehicle motion control intervention, and the vehicle motion is stable after the vehicle motion control intervention. The vehicle motion control device is characterized in that the parameter and the intervention threshold value are held at the previous values until it is realized. The vehicle motion control device according to any one of claims 1 to 5,
The estimated motion state quantity is at least one of a side slip angle and a yaw rate of the vehicle.

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